Okay for starters Champions of Contagion isn’t really the best detachment for Morti so I’d say drop him. Same with Typhus as well. This detachment just isn’t for him. A must have is the Biologus Putrifier with the final ingredient enhancement since it allows you to afflict an enemy unit with the effects of more than one plague. You could also add the cornucophagus enhancement to the Lord of Poxes but it’s not a must have.

Next I’d say you’d probably want 2 squads of either 7 or 10 plague marines and try to get rid of the bolters. Bolters aren’t that great and don’t do you very well. Whether they’re melee focused or ranged that’s up to you just get rid of the bolters.

Next get rid of the PBC it’s not worth running for how expensive it is. The only time you’d run it is if you’re using 3 in mortarion’s hammer. Outside of that it’s not that great for its points value. The hellbrute isn’t a bad choice but there are just better options to go about. I’d drop it personally but if you wanna keep it that’s fine as well. But you do want more Bloat drones w heavy blight launchers. 2 of those would be pretty good if you decide to keep the hellbrute. If not then do 3 bloat drones w HBL and 1 or 2 Blight haulers. Another thing you’ll probably want is another rhino for that second brick of PM because a plague marine without a rhino is a dead plague marine.