thank you.did you fix problem or still working on itI have this going on with mine, and from what I understand it's due to low nutrient levels, more specifically nitrogen and phosphorous.
Keep in mind I'm still new to all the chem with pants in a aquarium but I believe this is right,
and welcome to TPT.
iam getting the spots on the old leafs,new growth is redish green very nice new growth. i think my problem is not enough phosphates i was dosing 1 cap of florish phosp,i ordered some KH2PO4 from green leaf i also noticed spot alage is starting.the co2 is at 4 bps through a external reactor and drop checker is green. my new light i got is 6 x18watt t5ho which is highlight but its a 29 inch high tank.iam going to adj my n&p when i get my dry phosphate.i dont know what one cap ful is equivalent to, but i am almost positive that it is not as much as 1/8 tsp. of dry fert.my other plants are growing like crazy, old groth on them are ok. are you having the same problem?yes iam using csm+b with seachem iron also.Are you getting the black spots on new leaf or the older ones? Are you using micros also?
yea i know that very high light ,once plants grow in i will cut it down .i inspected leaves today it is not a algae its pinholes starting .was reading deficiency seems it might be potassium ,i think .i know the lights are running the plants into over time ,but only have a slight problem with GSA.turned up co2 a little more i will see what happens.(K is very mobile and signs first appear in older leaves, this can turn uniform yellow before they die. Pinholes appear in them and slowly enlarge. The new leaves are reduced in size and leaf area)6-T5HO bulbs will give very high light intensity on a 29 inch high tank, unless they are located in three rows of 2 bulbs per row. That will make controlling algae a continuing difficult problem. Black spots on old leaves in a high light tank is usually BBA, which is difficult to eliminate without having the CO2 concentration as high as the fish can live with, along with very good water circulation in the tank, non-limiting dosages of all of the nutrients, and meticulous tank maintenance.