A. Try restarting the game. Close the app completely by swiping up from the bottom of the screen (or double-clicking the home button) and swiping the Just Blocks app off the screen. Then reopen the app to see if the glitch persists.
B. Clear the app's cache by going to Settings > General > iPhone Storage, finding Just Blocks, and selecting 'Offload App'. This will remove the app but keep its documents and data. Reinstall the app to see if this resolves the glitches.