Here is an update. I have replaced the bacopa with Mayaca Fluviatilis (which has grown like crazy), removed the wisteria and replaced some of the dwarf sag with pelia. The guppy grass is gone as well.
I got the rocks from ebay, just search for lava rocks. Interestingly, I have these rocks in 2 different tanks, and the plants are doing a lot better in these 2. The nitrates are really low too with the rocks, in the shrimps tank they are actually 0. I suspect that lava rock has nitrates-removing properties.