Answer: Marathon is reasonably shade tolerant but it is slow to establish and doesn't like to be overwatered. It doesn't sound as though your grass seeds were able to develop a deep rooting system (soil compaction? too frequent watering?). If you prepared the soil well prior to seeding, the roots should be able to penetrate the soil and become well established. Without being able to examine the grass and the soil, I can only suggest that you rake, overseed, water frequently until the seeds sprout, then gradually reduce watering until you're only watering once each week. One deep soaking should per week should make your Marathon grow and thrive.
Best wishes with your lawn!
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