Both tanks are 10 gallons and same dimensions.
Tank 1 plants:
Crypt red wendtii
Anubias Afzelli (I think, trimmed down to nothing so will be a while before a positive ID can be amde)
Tank 1 growth is absolutely awesome, tank two all plants struggle. Tank ages within 6 weeks of each other with tank 2 being older.
NO3 10ppm, PO4 .77ppm, K 15ppm Sun, Tue, Thur
CSM+B to 0.3ppm iron Mon, Wed, Fri
Mg 10ppm and Calcium 40ppm Sunday after water change
Excel 4ml Sunday after water change and 1ml every day
Lighting is same 48 inch fixture over both tanks evenly distributed. 80 watts with one daylight bulb and one plant grow bulb.
Filters are AC 20 HOB. Bulbs less than 6 months old.
Substrate is exoxy gravel with about 20% plain river run smaller gravel.
Both tanks have crushed coral for pH and KH.
When I test for PO4, NO3, pH, KH and GH the test results are indistinguishable. Tests always show right balance and never a deficiency in anything nor an excess.
Plants in tank 2 show no signs of any deficiencies at all, just stunted growth.
Can anyone tell me what I am doing wrong in the second tank?