No they are fine, they had great Syrians for a while. If you say it's a heart problem, there's only 2 explanations. It's clogged or not airtight. You said your rig is completely airtight, so the only realistic problem left is an obstruction. blow into the hose port and then into the purge valve.
If it is an air problem, you will be able to feel it and hear it.