A diet of flake and bloodworm isn't all that great IMO; not just on their own anyway. Both have tendency to cause fish to bloat.
You could try getting the guppy into a net hung in the tank so it's in shallower water, that sometimes helps. Feed some lightly cooked, shelled, crushed pea if it's eating.
Try feeding a crisp or granule food and some frozen brine shrimp or daphnia as well in the future.
Hope he gets better.