I don't know enough about dosing it, so I looked it up
You said you've done, or are going to do, 3 treatments
On their site I found this, just in case you missed it;
A single treatment lasting 5-7 days is normally sufficient. Repeat as necessary, but no more than once every 3 to 5 days
If this isn't working for you, check out
this thread as there are 2 other recommended meds for other intestinal stuff that Prazi may miss
If you do end up using Seachem's Metro, mix it in a dish with some tank water and with Seachem's Focus to make a paste. This will bind it together and entice the fish to eat it
Once mixed it goes straight into the tank - no waiting
When I used it, I did this and also mixed some brine shrimp into it and it was all eaten before it had a chance to disperse
Hope it works out for you !
PS
If you do switch meds, it probably wouldn't hurt to do a WC first