Just start dosing EI. Use Chuck Glads calculator on the web to get the amounts. Start a little shy of the amounts that are calculated. If you light isn't high and you're not pushing your CO2 close to the warning levels for your fish, you may only need to dose once or twice per week. Flourish Excel could help if you don't have good CO2. Regardless, you only need kH and pH test kits.
If your plants are dying, your water changes are going to be critical. Change your filter more often as well.
I've had a dead tank. It will take some time to recover.
Andrew, MASI Treasurer
This message is always under construction: 75-gallon tank; 2, Eheim 2026 filters - one twice broken; Tek Light with 4, 54W T5s (6000K) ; Sand on top of 4:1 sand:clay mixture; Milwaukee CO2 controller; PlantGuild vortex CO2 reactor; pH = 6.6, kH=70mg/l, GH=120mg/l; EI; Flourish excel on 50% weekly water change: AGA Member.