I haven just returned from North Carolina where the forcythia is glorious. My plants here in Dallas are a poor example of what these beautiful spring shrubs can be. Help!
Check your pH asap and have soil tested. Digging in humus works wonders. My forsythia blooms in Jan/Feb in Fort Worth. It grows like a weed here. Maybe you missed the bloom period of yours in Dallas. If the leaves are yellow, it may be an iron deficiency.
Also, if it wasn't watered during this winter drought - that would account for poor spring development.