Multiple issues have added to the point that the scale tipped and the tank is getting choked by algae feeding on the failing plants.
Beyond the short term in my experience without the regular addition of fertilizers either water dosed or root tablets EC by itself didn't support plants very well. BBA does seems to like attaching to it though. Personally don't care for it after setting up one tank using it.
Yes you're light bulbs are losing spectrum but the 5 week lax period tipped things badly.
Using 10ml syringes I directly inject Glut or Hydrogen Peroxide (3%) on problem areas to kill BBA and other algae. With the water calm that creates a concentration well above what I would apply to the tank overall. Algae spot treated is quickly killed taking months to appear again. Excel does aid higher plants and it kills algae.
Valuable product to have on hand.
If by life's hectic schedule I neglect a tanking system and algae attacks my plants glut is the bomb. Water changed, parameters set and daily dosing of up to 10ml/15gal of tank volume to cover all areas with a treatment wipes the tank clean in a week or two then the jug is back on the shelf.
Daily use of it though I challenge the value as it relates to the need.
If lighting levels require regular additions of glutaraldehyde (Excel) to avoid algae I firmly believe you're tank and bank would benefit by adding pressurized CO2 injection and a down flow reactor. Recovery of costs would be achieved over a short time period. Same considerations switching to dry fertilizer. Anything stopping the shipment of pretty bottles of weak solution benefits the wallet.
I prefer dosing fertilizers in liquid form rather than the dry chemical. Fish can act darn stupidly and mouthing or eating Potassium Nitrate (KNO3), Mono Potassium Phosphate (KH2PO4), Potassium Sulfate (K2SO4) or Plantex CSM+B is a concern I have for them dry dosing. Probably thousands dose dry world wide without issue. I use to add it all dry but on accident dosed with the pumps off and the water calm. The chemical salts sank and landing on the plants in concentrate. Burned the plants killing growth to the base node. I've lost young fish that were seen grabbing the granules and spitting it back out. Quit dosing dry when I foolishly (in a hurry on my schedule) did it more than once. Who here is perfect? Pumps turned off to feed the fish I've later gone to bed forgetting to turn the filter back on. Nothing perfect about me.
Keeping planted aquariums long term using dry ferts are also HUGE savings over pretty premixed water bottles. $20 buys most enough plant food to last over a year. Why not just buy the bottles only once?
The basics for doing it are laid out by others in many formats. I liked this one starting out.
Common sense applies to everything (or should) DO NOT ORDER FROM Rex WITHOUT DIRECT CONTACT! His site store is active but he has not been in over a year. Orders are not filled.
Last activity 12/8/2010. But the tanking guide is a great reference starting out.
Ratios by gram and spoon measurements are provided on his site for those wanting to understand weed tanking step by step.
I would trim the ratty plants, vacuum mum and debris out of the tank changing the water. Get the ferts back up to feed the plants and order new bulbs.
Don't be a cow in the herd not knowing why is my message I guess (and don't trust Wikipedia and web forums LMAO!) without verifying information.
Ask what, ask why.
I've messed up my tanks more than once and brought them back.
Want to also add only 3 of my tanks are CO2 injected and with good ferts and understanding the light energy good tanks with healthy plants can be had without gas.
Hope ya fix you're water box without dumping it.