I find mixing glute in a spray bottle with some tank water does the trick. Spray all the exposed plants/hardscape when doing a water change and within a week or so the stuff is defeated. Leave it to soak for say ten minutes and then fill. I used to spot dose but it is too long and tedious if you have a lot of affected areas. Combining this with the increased maintenance you are doing should do the trick hopefully.
tank still looks great by the way, a proper nature aquarium!
Curious - What is a 'Glute spray'? Tried Googling Glute / water mix, and all I get is a selection of swimming exercises for strengthening buttocks!!