That stuff (ADA super clear) is supposed to help with "growing" BB and for removing organic substances. It sounds like they think your cycle crashed. The pic looks like a bacterial bloom perhaps. And you were going to post params for the tank but don't see them.
You could have:
1) dead or decaying plants
2) excess food leading to bacterial growth
3) crashed cycle
4) excess phosphate
5) some combo of the above
if you have params that you just took (not before it looked like this) it might help rule stuff out.
Not having that, since you've done 2 50% WC recently with no dissipation, it appears to be something that is either in the tank and you haven't removed, or is regenerating after the WC. That would lead me to either 1), 2) or 3). Since you said the params (assuming ammonia, nitrite and nitrate) are perfect, that rules out 3). So you may have a dead plant that is decaying or a bacterial bloom.
The latter is notorious for this behavior since the free floating bacteria can reproduce exponentially in conditions of high food (uneaten food or a dead fish.)
Did you vacuum the tank thoroughly in either of the WC you did?
